Torque Cars

UNF better than metric?

Discussion in 'Technical forum' started by old-git, 16 March 2012.

  1. old-git

    old-git Moderator

    Messages:
    9,182
    From:
    Essex
    Car:
    Elan & Robin Hood
    I have discussing with my chassis builder this afternoon about modifying my rear bottom wishbones, fitting rose joints so the toe in/out can be adjusted. The top wishbones were made to be adjustable during their manufacture.

    He said that I should use imperial UNF threaded joints rather than metric as they are stronger size for size. This is due to the depth of the thread being less on a UNF bolt than the metric equivalent. Apparently, F1 teams still use imperial rather than metric where strength is an issue for this very reason. I guess it also means that smaller diameter bolts can be used resulting in less weight.

    Can anyone confirm this?
     
  2. T9 man

    T9 man TC Pro Founder Moderator

    Messages:
    20,369
    From:
    London, UK
    Car:
    Saab 9-3SS T9
    I would be interested in hearing the answer to this one also! Still trying to get too grips with an F1 team (Technology Junkies) resorting to some Imperial materials :amazed:

    There's still hope for the old ways after all ;)
     
    Last edited: 16 March 2012
  3. Yugguy

    Yugguy Torque King

    Messages:
    4,787
    From:
    Rugby (expat Preston lad)
    Car:
    Merc C220Cdi Elegan
    Why doesnt someone just make shorter metric ones?
     
  4. old-git

    old-git Moderator

    Messages:
    9,182
    From:
    Essex
    Car:
    Elan & Robin Hood
    It's not the length of the bolt, but the depth of the thread.
     
  5. old-git

    old-git Moderator

    Messages:
    9,182
    From:
    Essex
    Car:
    Elan & Robin Hood
    They will use what is best for the job, regardless of how old it is.
     
  6. Yugguy

    Yugguy Torque King

    Messages:
    4,787
    From:
    Rugby (expat Preston lad)
    Car:
    Merc C220Cdi Elegan
    lol.

    Ok, why doesn't someone make deeper threaded metrics?
     
  7. old-git

    old-git Moderator

    Messages:
    9,182
    From:
    Essex
    Car:
    Elan & Robin Hood
    Deeper threaded metrics would be even weaker!! The deeper the thread the weaker the bolt.

    Thread sizes and design are now so deeply standardised that they won't be changed. For almost all purposes, metric thread design is fine. For specialist work where stength and weight are the important factors, there is already a perfectly good thread, UNF :)
     
  8. SLEEPER

    SLEEPER Pro Tuner

    Messages:
    2,782
    F1 cars treat weight as king in every department.
    I had never thought about metric v UNF but now I have it makes pefect sense
     
  9. Yugguy

    Yugguy Torque King

    Messages:
    4,787
    From:
    Rugby (expat Preston lad)
    Car:
    Merc C220Cdi Elegan
    Ah, I get it. To have shallow threaded bolts you'd need shallower threaded holes in all your engines.
     
  10. Charliep

    Charliep Torque Junkie

    Messages:
    125
    From:
    Thurrock, UK
    Car:
    Alfa GTV & 33
    Your chassis builder is talking utter rubbish.

    The general rule is that a bolt will have reached its full tensional strength at the depth being equal to its diameter. Additional depth can be given for a variety of reasons, which range from assembly to maintenance. Whatever thread type is being used is immaterial.

    To increase the strength a material with a greater tensile strength should be selected.

    The added length has one added advantage. When adjustment is needed on a fairly regular basis or the the bolt/stud has to be taken out then damaging the top of the thread will weaken it (even if it is not being cross threaded wear will make connections weaker). Therefore added length comes in handy.

    Such constructions obviously add some more weight to it, which is in racing situation not desirable. But then living components is not an issue in racing.
     
  11. suzsx041

    suzsx041 Torque Junkie

    Messages:
    144
    From:
    Adelaide Sth.Australia
    Car:
    subaru forester s3
    if you have a look at both metric and imperial thread gauges there isn't any difference
     
  12. old-git

    old-git Moderator

    Messages:
    9,182
    From:
    Essex
    Car:
    Elan & Robin Hood

    I think you missunderstand what I am talking about :) I am not talking about depth or bolt length but about the diameter of the bolt between the bottom of the treads, the minor diameter of the bolt. For any given bolt diameter the minor diameter of a UNF bolt will be bigger than the equivalent metric bolt and, therefore, stronger.

    However, as any sheer forces should be concentrated on the unthreaded part of the bolt, I doubt that the improvement in strength is very much.
     
  13. old-git

    old-git Moderator

    Messages:
    9,182
    From:
    Essex
    Car:
    Elan & Robin Hood
    What do you mean by no difference?
     
  14. old-git

    old-git Moderator

    Messages:
    9,182
    From:
    Essex
    Car:
    Elan & Robin Hood
    No. The major daimeter of the bolt thread is the same, it's the thread's minor diameter that is bigger on a UNF bolt compared to the metric equivalent. So the hole will be slightly bigger :)
     
  15. Charliep

    Charliep Torque Junkie

    Messages:
    125
    From:
    Thurrock, UK
    Car:
    Alfa GTV & 33
    It depends on the pitch. The finer the pitch, the bigger the threads diameter.

    bolts are designed for different uses, which are tensional, torsional or sheer forces or a combination of them.

    The metric system has many applications that are not available in just any hardware shop.

    The metric standard threads are designed to have a balance between pulling out the thread and the bolt snapping. In theory it should happen at the same time.

    The applications work around the structural requirements. Whenever the strength can't be achieved within the accepted tolerances a different material will be sourced. Hence the all aluminium construction of the Audi A2 consited of 37 different aluminium alloys. For the same reason as well as others some bolts are standard pitch and others are fine pitch.
     
  16. old-git

    old-git Moderator

    Messages:
    9,182
    From:
    Essex
    Car:
    Elan & Robin Hood
    Agree. But UNF is generally finer than the equivalent sized metric thread.

    I have asked anther guy who restores F1 cars and he confirmed that they are built mainly from Imperial bolts. I have asked him why and will report on the answer.
     
  17. Charliep

    Charliep Torque Junkie

    Messages:
    125
    From:
    Thurrock, UK
    Car:
    Alfa GTV & 33
    When the thread is finer than the metric fine threads then you need a longer bolt as the thread can't take as much tension as the bolt (thread length needs to be longer than bolt width). The question is what you want to let go sooner if things are stressed over the limits or for safety reasons (i. e. accident).

    Most of the F1 teams have been based in Britain, where the UNF was the norm. Designs have therefore been UNF based and therefore are still being used.
     
  18. SLEEPER

    SLEEPER Pro Tuner

    Messages:
    2,782
    If there was even the smallest benefit of using any other thread over UNF you can be sure F1 would have changed.
     
  19. Charliep

    Charliep Torque Junkie

    Messages:
    125
    From:
    Thurrock, UK
    Car:
    Alfa GTV & 33
    The thing is, there isn't an advantage to use one or the other in general. Both can be made working evenly well, depending on application and approach.

    I am living engineering and not bothered with either of the 2c norms. What it boils down to is the material the threads are made of.

    About 25 years ago I had to make some special bolts for some equipment that is stressed for more (and used on a daily basis) at 30.000rpm. The original bolts were failing to often leading to some serious problems. I spent 2 whole days in a steel mill going through data sheets to find the right steel.

    25 years on we have many more available. The base material is where you start from.

    Talking about racing. F1 is extreme in on way. However, other sports and other applications are extremely demanding too. The stresses on LMPs are extreme and metric threads are being used. Having worked a lot with Brembo brakes I can tell that they are happily using metric. In truck racing they use metric as well, braking 6 tons of mass. The list goes on.

    It doesn't matter whether you use UNF or metric. I certainly would not convert a UNF designed part to metric or vice versa.
     
  20. SLEEPER

    SLEEPER Pro Tuner

    Messages:
    2,782
    Yawn....................................
    You really should spend more time reading what people have said rather than telling us how knowledgeable you are.

    I didnt even comment on if there was a differnce I simply said that regardless of why UNF was used originally they wouldnt use it now if there was something better
     
  21. Charliep

    Charliep Torque Junkie

    Messages:
    125
    From:
    Thurrock, UK
    Car:
    Alfa GTV & 33
    If you had thought about what I wrote you wouldn't have made such an immature comment.

    Threading goes back many hundreds of years. Standards only came in due to industrialisation. Different global powers standardised them differently.

    Rather than implying what my motives are, switch on the brain and use physics. You are speculating without understanding the full back ground. This is one great help for the thread. I am talking fact. If you would I would not have to do it.

    So, refrain from silly and insulting remarks and contribute to the topic, but with factual input not speculation.
     
  22. claymore

    claymore The Torque Meister

    Messages:
    1,888
    From:
    Shrewsbury
    Car:
    T-10k,
    Still waiting to hear what you do for a living and who you work for, so that we can all bow down before you and your superiour knowledge.
     
  23. SLEEPER

    SLEEPER Pro Tuner

    Messages:
    2,782
    I see you still have not read my post despite your reply

    The thing is I wasnt and still dont disagree with you (on the point there may be no difference in which is best)

    So why you have to tell me how much experience you have (again) is beyond me.
    Id also be interested where I imply anything to do with your motives -

    We dont bring up your "abundance of knowledge" you do .......................all the time.
     
  24. Charliep

    Charliep Torque Junkie

    Messages:
    125
    From:
    Thurrock, UK
    Car:
    Alfa GTV & 33
    It might have occured to you that forums are information bases. What is the point of having the knowledge when it is not being used? Unlike the ones who want to make believe that only the 'chosen' ones can do the work I am, I give my knowledge away.

    And to clarify this: If I make claims, I am being flamed. Yes, it has happened even here on the forum. When I bring proof I am going to be flamed because I am bragging.

    Where you imply my motives? In the the last sentence of the quote and in the first sentence of the previous quote.

    @ Claymore - Only idiots would bow down to me. Intelligent people go and make use of my knowledge. This is what knowledge is for.

    And why do you want to know who I am? This doesn't make a difference of what I am claiming is true or not. I am going with the test results I am colating. These tests don't lie and they aren't hear-say. They are hard facts and this is what this forum should be about.
     
  25. HDi fun

    HDi fun TC ModFather

    Messages:
    15,384
    From:
    Buckinghamshire UK
    Car:
    Passat 2.0 TDi
    I agree with CP that material selection is likely to be the single biggest factor. I am not a metallurgist, however.

    This is why, for example, long bolts such as cylinder head bolts are designed to stretch during installation and for the same reason they cannot be re-used. A hard but brittle material would be totally unsuitable in this application.

    One the other hand, a bolt that's simply used to clamp a jubliee clip is not really subjected to any forces at all other than extremely slight tension (stretching). In this case choice of material and thread pitch and depth are largely unimportant. Corrosion resistance would be the secondary goal. Cheap manufacture being the primary one.

    @CP, I don't think anyone's trying to attack you. Torque Cars is not like that in general. I agree many other forums are so I understand you appearing slightly defensive when you really have no need to be so. All that's happening is people are clamouring to understand what it is you're saying. They're not looking for justification in order to flame you or discredit you when you provide it. There's a thirst for knowledge here -something I see as credible given the general low level of intelligence we see during our daily lives.

    Welcome. It's good to have you on board.

    Best regards,

    Paul Anderson.
     
Loading...

Share This Page

Click Here
  1. This site, like pretty much every other site, uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are agreeing to our use of cookies, this may include third party cookies from our carefully selected advertising partners and for our analytics which allow us to see which pages are of interest and improve our site navigation and experience.
    You can disable cookies in your browser but this may affect your experience on this website.

    Dismiss Notice